摘要:

An electrostatic emission microscope operating with an accelerating voltage of 10–25 kv is briefly described. Factors determining image quality, particularly contrast and resolution, are discussed and the interpretation of images on the basis of the Schottky emission equation is considered. The instrument can be operated at magnifications of 250, 1000, 2500, and 4000× with a resolution consistently better than 1000 A.It has been found that the iron group metals can be activated easily using barium formate rather than evaporated Ba or Sr. The level of thermionic emission from such surfaces is determined primarily by the partial pressure of chemical reducing agent at the surface (such as carbon) to reduce BaO to free barium. The effect of various impurities and alloying metals is discussed from the standpoint of interpretation of emission images. The most important single agent for promoting emission from Ni, Cu, and Fe, etc., is carbon.Examples of emission images include nickel, stainless steel, and plain carbon steel. Complications such as surface roughness are demonstrated with micrographs and the limitations of the technique pointed out.

ISSN:0021-8979    

DOI:10.1063/1.1722084

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The strong‐shock, point‐source solution and spherical isothermal distributions were used as initial conditions for a numerical integration of the differential equations of gas motion in Lagrangean form. The von Neumann‐Richtmyer artificial viscosity was employed to avoid shock discontinuities. The solutions were carried from two thousand atmospheres to less than one‐tenth atmospheres peak overpressure. Results include overpressure, density, particle velocity, and position as functions of time and space. The dynamic pressure, the positive and negative impulses of both dynamic pressure and static overpressure, positive and negative durations of pressure and velocity, and shock values of all quantities are also described for various times and radial distances. Analytical approximations to the numerical results are provided.

ISSN:0021-8979    

DOI:10.1063/1.1722085

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722086

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722087

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722088

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722091

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722092

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722093

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722094

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722095

出版商:AIP    

年代:1955

数据来源: AIP